What a ratio at a stated temperature pins down
A coefficient of performance fixes a ratio at a moment: the heat a machine delivered, divided by the electricity it drew, under one stated pair of air and water temperatures. Measured properly it is not an opinion, and EN 14511 sets out how the measurement should be taken.
What it fixes is narrower than it looks. It fixes performance at those temperatures, on that day, at that humidity. It is a photograph, not a specification.
Why it is not a consumption
It does not promise a consumption. Nothing about a COP translates into kilowatt-hours over a season without knowing the weather, the pool, the cover and how warm you want the water — none of which a manufacturer knows and none of which this site will assume on your behalf.
It does not promise comparability. A COP of 16 at 26 °C and a COP of 5.5 at 15 °C can belong to the same machine, and two listings quoting those two figures look like two very different products. Where a maker publishes only the warm-condition figure, the page says which condition it belongs to and leaves the cold-condition line empty rather than filling it in.
And it does not promise that heating is worthwhile. A cover changes the arithmetic of a heated pool more than a higher COP does, because most of the heat a pool loses goes out of its surface overnight. That is a published behaviour of covers, not a calculation of ours.
The three figures a COP travels with
Three figures beside it, and the page prints them together where a maker gives them. The heating output in kilowatts, which says how fast rather than how efficiently. The rated volume, which is the maker’s own statement about the size of pool the machine was built for. And the noise level in decibels at a stated distance, which decides whether a machine can run at seven in the morning without a conversation with a neighbour.
Inverter models publish a COP range rather than a point, because the compressor modulates. Where that is the case, the page reports the range as published and the conditions at each end.
Where a COP appears, and where it does not
Heat pumps, where the COP is the headline and the conditions are usually in a table further down the page. Electric heaters, where there is no COP to speak of — an immersion element is close to 1 by construction, and a listing that quotes anything higher is describing something other than resistive heating. And solar collectors, which publish no COP at all and are compared instead on absorber area and the temperature lift a maker states for a given flow.
What readers keep writing in to ask
Why is a COP of 16 even possible?
Because a heat pump moves heat rather than making it, so the output can be many times the electricity consumed. Sixteen is a genuine ratio at a genuine pair of temperatures — warm air and already-warm water, where the machine works least hard. It is not a fraud; it is a measurement of the easiest case.
What conditions should I look for?
Whichever ones the maker published, because that is the only pair this site can report. Where a listing gives several — commonly a warm pair near 26 °C and a cooler pair near 15 °C — the page prints both, and the cooler figure is the one that describes an April morning.
Does EN 14511 make COPs comparable?
It defines how the measurement is taken, which is a real contribution. It does not oblige a seller to state which conditions a headline figure came from, so two listings can both be accurate and still be incomparable. That gap is what this page exists to name.
How does this site handle a COP with no conditions?
It prints the figure and records that no conditions were published, in the same row. It does not estimate what they might have been, and it does not drop the figure — an unqualified COP is itself a finding about the listing.
Last reviewed 21 September 2026